The load was worked up in a Browning BDA (early Sig P220), and showed NO pressure signs in that particular gun. Yes, the load was hot rodded, but the Speer Number 9 manual (what was current at the time) lists max as 7.3gr for that bullet and Unique. So the load wasn't as far above the listed max then as it is today.
I never intended the load for use in any other guns, nor for continous use in the BDA. Had some at the range, and a friend (action/pin shooter) asked to try some. After warning him, I gave him one mag's worth. I wouldn't do that today, but 20+ years ago people were generally less lawyer prone.
The load functioned fine through his gun, but the primers did crater, intidicating thge load was too warm for his gun. I believe this is a clear indication of the differences that different guns will tolerate, and I mention it solely for illustrative purposes. I did not recommend loading to this level. Only that I once had, and found it not suitable for some guns.
All else being equal (and it almost never is) bigger bullets tend to work better.